Device for drying the blanket cylinders in offset printing machines



y 1959 w. KOCH 2,884,855

DEVICE FOR DRYING THE BLANKET CYLINDERS IN OFFSET PRINTING MACHINESFiled June 1, 1955 77a 77b 73/ 1e @8 ra 60 lid 2/ I? 73 5 PM MA.

Inventor UnitedStates Patent DEVICE FOR DRYING THE BLANKET CYLINDERS 1NOFFSET PRINTING MACHINES Werner Koch, Oifenbach (Main), Germany,assignor to Faber & Schleicher Aktiengesellschaft, Offenbach (Main),Germany, a German body corporate This invention relates to the blanketcylinders of olfset and the like printing machines and more particularlyto the means which are used for drying the blankets of these cylindersfrom adherent moisture by means of air.

In this type of machine it is almost impossible to avoid the blankettaking up moisture from the nonprinting parts of the plate and itstransference to the material to be printed upon. If this materialhappens to be of a hygroscopic nature, such as sized paper for instance,or composed of certain resinous substances, this moisture is eagerlyattracted with the result, that the material begins to warp so that itbecomes almost impossible to obtain a correct register. Thisdisadvantage is particularly noticeable in connection with multiplecolor printing machines, when there is no possibility of the printingmaterial disposing of the absorbed water prior to the application of thenext color.

Devices have been proposed for the purpose of drying the blankets by airblown against them and toincrease the surface action of the blast byheating. However, such devices were unable to produce thedesired efiectexcept under certain, very limited conditions, since in every instanttheir water absorbing capacity depends on the moisture which iscontained in the drying air. Heating of the air is applicable only to avery small extent because of other difiiculties which would arise fromthe transmission of the heat to the surrounding parts of the machine andeven to the whole of the machine.

It is, therefore, the main object of the invention to provide a devicefor air-drying the blankets in ofiset printing machines in which theaforesaid disadvantages are avoided by circulating the drying air in asubstantially closed conduit through which it is forced incircumferential direction over preferably the whole width of the blanketcylinder and in a manner in which the part of the blanket which issubjected to the air would form a part of the walls of the said conduit.

Another object of the invention is the provision, within the closed airconduit, of means for thoroughly evaporating practically all themoisture which the drying air has taken up during its circulation in amanner which ensures of the air becoming almost entirely free from anywater or vapours independent of the moisture contents of the surroundingair, and to thus acquire a particularly high capacity for absorbing themoisture from the blanket cylinder.

A further object rests in so devising the drying means in the aircurrent that they will only have to dissipate such vapours which areactually absorbed from the blanket and to thus ensure of the said dryingmeans retaining their water evaporating capacity for a considerableextent of time and to remain fully effective also at low roomtemperature.

A still further object of the invention is the provision in the said airconduit of vapour dissipating means in which a multiple arrangement ofsuch means is provided, in which one of these elements will always befree for the passage of the drying air therethrough, while the other iscut out of the circulation and thus given time to recuperate. Heatingdevices may be provided to accelerate the evaporation of the moisture.

With these and other objects in view the invention broadly consists in adevice in which a fan or ventilator is provided to circulate a stream ofair through a substantially closed pipe system, of which one part isconnected to a distributor or shield which extends over a part of thecircumference of the blanket cylinder and over practically the fullwidth thereof, and through which pipe system and distributor or shield,the moist air from the blanket is circulated. A heater which may beprovided in the system keeps the circulating air at a comparatively hightemperature to facilitate its drying action on the blanket.

In accordance with the invention the said pipe system is provided with afilter in which the moisture, which is taken up from the blanket of theblanket cylinder, is re tained and dissipated, or evaporated, as forinstance by the application of electric heat. The filter or dryingdevice for the circulating air comprises a cylindrical or otherreceptacle which is filled with a porous, moisture absorbing material,such as infusorial earth for instance, through which the humidified airfrom the blanket cylinder is passed.

In order to further increase the efiiciency of the device the inventionprovides for preferably a multiple arrangement of such filters, of whichalways at least one will be in communication with the pipe carrying themoisture from the blanket cylinder to the ventilator while the other, orothers, is at rest. Its connection to the system is interrupted so thatthe material therein is given ample time to dry. An electric heatingsystem may be provided to accelerate the evaporation of the moisture andthe vapours are allowed to escape into the atmosphere. Interconnectedmultiway valves or cocks are provided to connect either the one or otherof the devices into the drying air current.

It is evident that only a small quantity of air will be required fordrying the blanket cylinder in accordance with the invention, which airis circulated by a comparatively small ventilator so that the wholeinstallation remains of a moderate size. Further advantages are its lowcosts of production and maintenance and, notwithstanding, its highefficiency in use.

The accompanying drawings diagrammatically illustrate the invention byway of example. In these drawings,

Fig. 1 shows an air circulating system having two air drying or filterunits with one of them in connection with the air circulating means andthe other one at rest, and

Fig. 2 illustrates the position of the device with the other filter unitin the system and the former at rest.

The numeral 1 denotes the blanket cylinder of an ofiset or similarprinting machine, while 2 is a ventilator, the pressure side of which isconnected by means of the pipe 3 to a removable air heater 4, in which apreferably electric heating element 4a is provided for the heating ofthe air flowing through the system. From the heater 4 a pipe 5 leads toa distributor or shield 6 through which it passes in form of a loop 7closely following the curvature of the circumference of the blanketcylinder. The distributor 6 extends laterally over practically the wholewidth of the cylinder. At the side facing the blanket cylinder both thedistributor and the loop 7 are open so that the blanket 8 actually formsthe back wall of both the distributor and the loop at that place of thecylinder, leaving only a very thin space which, in addition, is providedwith packing grooves 9, so that losses of air are practically avoided.

From the exit side of the distributor 6 a pipe 10 leads over a multiwayvalve 11 to a drying set which consists of two units 12 and 13 filledwith a suitable hygroscopic material, such as infusorial earth, and fromthere over a #3 threeway valve 14 to the suction side of the ventilator2. In the position shown in Fig. 1 the valve 11 is turned so that itspassage 11a connects the pipe to the drying unit 12, whereas the unit 13is disconnected from the pipe 10. In this way the filter unit 13 isplaced at rest so that the hygroscopic material therein is allowed todry, the vapours escaping by the passage 11b of the multiway valve 11through the open socket into the atmosphere.

In Fig. 2 the position is reversed, the unit 13 in this case being incommunication with pipe 10 through the passage 11b While the threewayvalve 14 connects it through the passage 14b to the ventilator 2. Itwill be seen from Fig. 2 that this time the other unit 12 is at rest andthat the vapours are allowed to escape through the socket 19. The dryingunit 12 is provided with a heating resistance and the unit 13 with asimilar heating resistance 21 through which the evaporation of themoisture from the filter material in the drying units can be expedited.

The valves 11 and 14 are provided with levers 16 and 17 respectivelywhich are connected to one another by a hand bar 18, by which either ofthe drying units 12 or 13 can be connected into the circulating systemwhile the other is allowed to recuperate. Instead of the hand bar 18 thelevers 16 and 17 may be connected to a driven part of the printingmachine.

What I claim is:

1. In a device for drying the blankets of the blanket cylinders inoffset and the like printing machines by air draft, a substantiallyclosed pipe system, a ventilator for circulating air through the saidpipe system, a loop formed by one of the pipes in the said systemarranged approximately to follow the curvature of the blanket cylinder,an open side to the said loop facing the blanket, a shield receiving theopen part of said loop for confining the air traversing the loop at thevicinity of the blanket, means in connection with said shield to preventthe influx of room atmosphere into the closed pipe system, filter meansin connection with said pipe system for absorbing the moisture taken upby the circulating air from the blanket, and a heating device in thepipe system for heating the circulating air prior to its action on theblanket cylinder.

2. In a device for air-drying the blankets of the blanket cylinders inoffset and the like printing machines by air draft, a substantiallyclosed pipe system, a ventilator for circulating air through the saidpipe system, a loop formed by one of the pipes in the said systemarranged approximately to follow the curvature of the blanket cylinder,an open side in the said loop facing the blanket, a shield receiving theopen part of said loop for confining the air traversing the loop at thevicinity of the blanket, means in connection with said shield to preventthe influx of room atmosphere into the closed pipe system, a filter inthe said pipe system for absorbing the liquid collected by thecirculating air from the blanket, a housing for the said filter, aquantity of absorbing material in said housing for drying the aircirculating therethrough, and pipe sockets for connecting said housinginto the said pipe system.

3. In a device for drying the blankets of the blanket cylinders inoffset and the like printing machines by air, comprising, a closed pipesystem, a ventilator for circulating a volume of air through the saidpipe system, a loop formed by one of the pipes in the said systemarranged to follow the curvature of the blanket cylinder, an open sideto the said loop facing the blanket, a distributor shield to receive theopen part of said loop and extending over the full width of the cylinderto confine the air traversing the loop at the vicinity of the blanketand to prevent influx of room atmosphere into the closed pipe system, aplurality of drying filters in the pipe system, means for selectivelyconnecting one of the drying filters into the stream of the circulatingair while allowing the other, or others, to remain at rest, and aheating device in each of the said drying filters for accelerating theevaporation of the moisture absorbed by the said filter from thecirculating stream of air.

4. In a device for drying the blankets of the blanket cylinders inoffset and the like printing machines by air, comprising, a closed pipesystem, a ventilator for circulating air through the said pipe system, aloop formed in one of the pipes in the said system arrangedapproximately to follow the curvature of the blanket cylinder, an openside in the said loop facing the blanket, means in connection with thesaid loop for preventing the influx of room atmosphere into the closedpipe system, a twin set of drying units in the pipe system intermediatethe cylinder and the suction end of the ventilator, a multiway valve toselectively place either one of the said units into communi cation withthat pipe of said pipe system which leads from the blanket cylinder inthe direction of the ventilator, another multiway valve for placing theselected drying unit into communication with the suction side of theventilator, and means for actuating the said two multiway valvessimultaneously.

References Cited in the file of this patent UNITED STATES PATENTS1,757,948 Hockley May 6, 1930 2,002,815 Harrold May 28, 1935 2,083,732Moore et al June 15, 1937 2,676,536 St. Marie Apr. 27, 1954 FOREIGNPATENTS 584,240 Great Britain Jan. 9, 1947

